The exemplary embodiment relates to the printing arts. It finds particular application in connection with a printer and a method for safely extending the designated life of a customer replaceable unit.
Electronic printing systems, such as printers, copiers, multifunction devices, and the like, typically employ an input terminal which receives images in digital form and conversion electronics for converting the image to image signals or pixels. The printing system may include a scanner for scanning image-bearing documents or be connected to a computer network which supplies the digital images. The signals are stored and are read out successively to a marking engine for formation of the images and transfer of the images to a print medium, such as paper.
In typical electrophotographic printing systems, for example, such as copy machines and laser beam printers, a photoconductive insulating member, such as a photoreceptor belt or drum, is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within the document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with a marking material. Generally, the marking material comprises toner particles adhering triboelectrically to carrier granules, which is often referred to simply as toner. The developed image is subsequently transferred to the print medium, such as a sheet of paper. The fusing of the toner image onto paper is generally accomplished by a fuser which applies heat to the toner with a heated roller and application of pressure.
To facilitate replacement of components of a printing system which have an expected lifetime which is shorter than the expected lifetime of the printing system in which they are used, the components may be in the form of self-contained modules, often known as customer replaceable units (CRUs). Typical CRUs include imaging units, fuser units, marking material containers, such as toner cartridges, photoreceptor belts, and the like. The CRUs are designed to make the replacement of replaceable components easy for the end user to perform. CRUs typically have an end of lifetime (EOL) which may be based on the expected lifetime of the CRU, in terms of the number of prints made or other determinable parameter.
The EOL is generally based on prior experience and is selected to avoid the risk of a component reaching a state in which it may negatively impact image quality or printing capability, or cause damage to the printing system in which it is used. For example, wear on the photoreceptor drum or belt, which is typically related to the number of prints made, not only can result in visibly defective prints but may lead to damage of other components of the printing system, for example, causing a failure of the developer housing. The EOL for an imaging unit CRU, which includes a photoreceptor as well as other components, may therefore be selected to ensure that there is little or no risk of either of these events occurring. Fusers also tend to have a restricted lifetime because of the high temperatures used, particularly in color printing systems. Fusers can fail catastrophically or may suffer a partial failure leading to problems in other components of the printing system, such as causing paper jams due to inadequately fused toner. Stripper fingers can wear, leading to jams. Thus the EOL of a replaceable module is selected to avoid such occurrences. Once the EOL is reached, the printing system is automatically shut down.
Because many CRUs are expensive components, it is undesirable for a customer to have to keep a supply of CRUs on hand for replacement when an EOL is reached. Accordingly, printing systems are designed to provide the customer with a reorder message when the EOL is approaching, giving the customer the opportunity to order a CRU before the EOL is reached. However, if the customer fails to notice or ignores the message, or if there is a delay in shipment of the replacement CRU from a supply center, or a CRU does not reach the correct destination, when the EOL is reached the machine will cease functioning, often resulting in significant downtime or customer dissatisfaction.